1. Field of the Invention
The present invention relates to an expansion tool device for pliers or a machine for producing sockets at the ends of pipes made out of plastic material or out of composite materials of the type commonly referred to as multi-layer material, used in the field of plumbing.
2. Description of Related Art
In a known way, a socket, whether on a copper pipe or a pipe made out of plastic or composite material, is produced by means of manual pliers or a machine for producing sockets provided with an expansion tool that includes a cylindrically shaped ferrule formed by the tightening of several sector-shaped chucks movable in the radial direction. The nearing to each other of the legs of the pliers, or the actuation of the machine causes the axial displacement of a tapered needle between said chucks, causing the latter to move apart.
A socket on a plastic pipe or composite pipe is not produced entirely like a socket on an annealed copper tube. Indeed, the end of the pipe should be sufficiently widened in order to allow the fitment before it recovers its shape. Furthermore, for obvious reasons of strength, the thickness of the wall of the pipe increases as the diameter of the latter increases, and the more the thickness increases, the quicker the elastic recovering occurs, which requires a larger widening.
Now, during the expansion, the chucks separate from each other, which creates between them grooves into which the material penetrates so as to create internal turgidities. This deformation results into an imperfect fitment likely to cause leaks.
In order to cope with this disadvantage, although it is not possible to completely eliminate the formation of turgidities, there has been proposed, namely in European Patent No. EP0718057 and European Patent No. EP0878287, to machine the edges of the chucks so as to limit the deformations. Thus, in the first document, the edges are broken by forming a chamfer or a rounding-off, while in the second document the working surface of each chuck has at the level of each of its longitudinal edges a flat surface at right angles with respect to the side of said chuck, adjacent to said working surface.
However, in practice, in order to cope with this disadvantage, users proceed to a series of widening operations, each together with an axial swiveling of the tool with respect to the pipe, so that, at each expansion, the turgidities created during the preceding expansion are flattened. Though this does not allow eliminating completely the turgidities, it reduces their effects.
Though this way of operating allows using the traditional tools, it can prove delicate and difficult to be performed at some locations of limited access. In addition, it requires some attention from the user, who may not forget to rotate the tool, but must also take care that, upon rotation of the tool, the chucks are properly arranged in front of the previously created turgidities. This way of operating is thus at random and therefore likely to maintain the risk of leaks.
It should be noted that there is also known, from Japanese Patent No. 57 009541, an expansion tool having a tapered needle of which is provided with helical grooves, which catches the chucks included on their inner faces, being cooperative with the grooves, so that the axial displacement of said needle causes not only the radial separation of said chucks, but also their axial rotation. The widening is thus achieved through two conjugated movements of separation and rotation, which requires, on the one hand, special means for maintaining the tube, in order to prevent it from rotating, and powerful driving means, in this case hydraulic means, for transmitting, during the radial displacement of the tapered needle, a rotational motion to the chucks. The radial displacement is thus always associated with an axial rotation, either during the separation from or the nearing to each other of the chucks. Furthermore, such a tool requires the needle of the tool as well as the chucks to be of a particular design, whereas one of the objects of the invention is to allow using chucks of a traditional design.